Core 3 Abstract To ensure reproducibility, rigor and harmonization amongst the mouse glioblastoma (GBM) models utilized by Projects 2, 3 and 4, we have established a mouse GBM model Core that is exclusively utilized for this Program Project and does not exist within participating Institutions. The Core provides broad centralized access to a central repository responsible for the maintenance and testing of mouse GBM tumors and professional expertise related to their stereotactic implantation into mouse brains and the analysis, including imaging of intracranial GBMs. It also has been providing mouse GBM neoantigen discovery and validation. This would include access to mouse cell lines and their derivatives critical to the experimental aims. This is more easily accomplished through the Core and not as easily done through individual (e.g. R01) granting mechanisms or through existing NIH sponsored service cores at the P01 institutions. This will be accomplished by pursuing two specific aims: generate and maintain a repository of mouse GBM cells, engineer GBM cells that express transgenes of interest, and identify and validate mouse GBM neoantigens (Aim 1) and provide the technical expertise and performance for the stereotactic implantation of mouse GBMs in brains and for their serial imaging (Aim 2). The provision of these services for 3 of the 4 Projects will reduce expense, will reduce technical and sample bias and will ensure that the 3 Projects will employ the same well characterized mouse GBM cells that are implanted and imaged by expert technical personnel.